function changHoverImg() {
    var imgs=document.getElementsByClassName("imgs");
    for(var i=0;i<imgs.length;i++){
        imgs[i].index=imgs[i].src;
        imgs[i].oldClass=imgs[i].className;
        imgs[i].onmouseover=function () {
            var b=this.index.split("/un");
            var c=b[0]+"/hover_un"+b[1];
            this.src=c;
            this.className=this.oldClass+" changes";
        };
        imgs[i].onmouseout=function () {
            this.src=this.index;
            this.className=this.oldClass;
        };
    }
}

window.onload=function (){
    changHoverImg();
} ;